®React’s 15 Most Powerful Interview Questions React interviews in are no longer about memorizing hook names or JSX syntax. Interviewers now test performance trade-offs, architectural decisions, and real‑world problem‑solving. Here are 15 powerful questions asked in top product‑based companies — each with its level and a crisp answer. --- Level 1: Fundamental (Beginner to Mid‑Level) Q1. What is React Fiber and how does it improve rendering? Answer: React Fiber is a complete rewrite of React’s core algorithm. It enables incremental rendering, making the UI more responsive. Fiber splits render work into small units that can be paused, resumed, and aborted. This is why React can now support features like error boundaries, Suspense, and concurrent rendering. --- Q2. How does the reconciliation algorithm work? Answer: Reconciliation is the process where React compares the new virtual DOM tree with the old one and computes the minimum number of D...